This means that MTT will potentially have to test less stuff. More
specifically, MTT will only have a tarball to test when there is actually
something new to test. Hence, this can significantly decrease the
proability of their being 1.1 and 1.0 tarballs to test, and therefore lower
the amount of resources required for sites to test 1.1 and 1.0.

We used to generate new tarballs for all branches whenever there was even
one commit on any development/release.